1. Field of Invention
The present invention relates to a system for wireless direction-finding and location, and more specifically, to a system for improving the overall performance and power management in a wireless communication device performing a direction of arrival estimation.
2. Description of Prior Art
Modern society has quickly adopted, and become reliant upon, handheld devices for wireless communication. For example, cellular telephones continue to proliferate in the global marketplace due to technological improvements in both the quality of the communication and the functionality of the devices. These wireless communication devices (WCDs) have become commonplace for both personal and business use, allowing users to transmit and receive voice, text and graphical data from a multitude of geographic locations. The communication networks utilized by these devices span different frequencies and cover different transmission distances, each having strengths desirable for various applications.
Cellular networks facilitate WCD communication over large geographic areas. These network technologies have commonly been divided by generations, starting in the late 1970s to early 1980s with first generation (1G) analog cellular telephones that provided baseline voice communications, to modern digital cellular telephones. GSM is an example of a widely employed 2G digital cellular network communicating in the 900 MHz-1.8 GHz band in Europe and at 1.9 GHz in the United States. This network provides voice communication and also supports the transmission of textual data via the Short Messaging Service (SMS). SMS allows a WCD to transmit and receive text messages of up to 160 characters, while providing data transfer to packet networks, ISDN and POTS users at 9.6 Kbps. The Multimedia Messaging Service (MMS), an enhanced messaging system allowing for the transmission of sound, graphics and video files in addition to simple text, has also become available in certain devices. Soon emerging technologies such as Digital Video Broadcasting for Handheld Devices (DVB-H) will make streaming digital video, and other similar content, available via direct transmission to a WCD. While long-range communication networks like GSM are a well-accepted means for transmitting and receiving data, due to cost, traffic and legislative concerns, these networks may not be appropriate for all data applications.
Short-range wireless networks provide communication solutions that avoid some of the problems seen in large cellular networks. Bluetooth™ is an example of a short-range wireless technology quickly gaining acceptance in the marketplace. A Bluetooth™ enabled WCD transmits and receives data at a rate of 720 Kbps within a range of 10 meters, and may transmit up to 100 meters with additional power boosting. A user does not actively instigate a Bluetooth™ network. Instead, a plurality of devices within operating range of each other will automatically form a network group called a “piconet”. Any device may promote itself to the master of the piconet, allowing it to control data exchanges with up to seven “active” slaves and 255 “parked” slaves. Active slaves exchange data based on the clock timing of the master. Parked slaves monitor a beacon signal in order to stay synchronized with the master, and wait for an active slot to become available. These devices continually switch between various active communication and power saving modes in order to transmit data to other piconet members. In addition to Bluetooth™ other popular short-range wireless networks include WLAN (of which “Wi-Fi” local access points communicating in accordance with the IEEE 802.11 standard, is an example), WUSB, UWB, Bluetooth Low End Extension (BTLEE)/BluLite, ZigBee/IEEE 802.15.4, and UHF RFID. All of these wireless mediums have features and advantages that make them appropriate for various applications.
More recently, manufacturers have also began to incorporate various resources for providing enhanced functionality in WCDs (e.g., components and software for performing close-proximity wireless information exchanges). Sensors and/or scanners may be used to read visual or electronic information into a device. A transaction may involve a user holding their WCD in proximity to a target, aiming their WCD at an object (e.g., to take a picture) or sweeping the device over a printed tag or document. Machine-readable technologies such as radio frequency identification (RFID), Infra-red (IR) communication, optical character recognition (OCR) and various other types of visual, electronic and magnetic scanning are used to quickly input desired information into the WCD without the need for manual entry by a user.
Wireless communication devices employing the previously discussed characteristics may be used for a variety of applications other than basic voice communications. Exemplary applications for business may include scheduling, word processing, spreadsheets, facsimile transmission, contact management, etc. There is also a multitude of applications for the personal enjoyment of the user, such as games, instant messaging, display wallpaper, etc.
A wireless service provider may determine the current location of a wireless communication device by how it is communicating on the wireless network (e.g., by identifying the cell where a cellular phone last accessed the network). While the benefit of being able to locate a communication device in certain situations is apparent, such as in an emergency, the ability to provide location-related information to a user would also be a beneficial feature. Exemplary systems now envisioned might empower a user to determine current location using their WCD, and combined with other applications, may be useful for route or direction finding from a current location to another mapped location.
Current handheld location-finding systems that operate using services such as the Global Positioning System (GPS) are now available on the market. These standalone devices may provide bearings and directions to address locations or longitude/latitude positions. However, the bearings and directions may only be provided relative to the moving direction of the GPS device. Traditional GPS receivers will not assist a user who wishes to track an object tagged with a beacon (for example, an IR beacon on a keychain fob), or a destination that is currently unknown, such as access to public transportation or a hospital marked by an IR beacon. While solutions are now being devised that provide for these tracking features in a wireless communication device, just making the functionality available does not fully satisfy the need. A portable device, such as a phone or communication-enabled PDA, may be resource constrained (e.g., by a battery power source and small size). Conversely, a WCD that is constantly searching for a signal may consume considerable power, especially if, given the shrinking size of today's devices, there is little room for a substantial antenna array to receive locator signals. As a result, for a tracking application to be useful and effective, these device limitations must be considered.
What is therefore needed is a directional and/or location finding method and system that allows a user to track or locate a signal beacon using a direction of Arrival (DoA) estimation, while simultaneously managing the wireless communication device to optimize its performance. The DoA application should work in conjunction with various resources within the wireless communication device in order to provide a visual representation of the relative direction towards, or location of, an object, place, etc. maintaining a broadcast beacon. The functionality should further utilize information from one or more sensors within the device to affect the behavior of the device, for example, by controlling the DoA functionality and/or application, quality measurement of the DoA estimate, power management of the device, etc.